In today’s modern high-stress environment, cortisol is often referred to as the “stress hormone,” but its role in the body is far more complex than most of us know. Produced by the adrenal glands in response to both good et bad types of stress (think going on a first date or playing in the big leagues vs being diagnosed with a disease or involved in a car crash), cortisol affects various physiological functions like exercise, et plays a pivotal role in numerous body systems, including metabolism, immune function, and—of course—the body’s stress response.
Although cortisol is essential for survival and homeostasis (keeping your body’s systems “balanced”), too much cortisol for too long can negatively impact multiple body systems. Let’s take a look at what cortisol does in the body, the potential consequences of cortisol imbalance, and how hormonal birth control may affect cortisol levels.
How cortisol is made in the body
Cortisol is primarily produced in the adrenal cortex, which is the outer layer of the adrenal glands located on top of the kidneys. Cortisol is regulated by the hypothalamic-pituitary-adrenal (HPA) axis, which maintains homeostasis and helps the body respond to stressful situations.
When the brain perceives stress, two systems are activated. One is the sympathetic nervous system, which includes the fight-flight-freeze response we’re all familiar with. The second system is the HPA axis. When activated, the first component of the HPA axis, the hypothalamus (the part of the brain that regulates body temperature, hunger, mood, blood pressure, and sleep), releases corticotropin-releasing hormone (CRH) [1]. The release of CRH in turn stimulates the pituitary gland to release adrenocorticotropic hormone (ACTH) which then signals the adrenal glands to release cortisol into the bloodstream.
Cortisol levels naturally change throughout the day
Cortisol follows a diurnal rhythm in healthy individuals. This means that levels peak in the early morning and gradually decline throughout the day. This cycle, known as the cortisol awakening response (CAR), sees cortisol levels rapidly increasing in the first 30-45 minutes after waking up in the morning, which is essential for promoting alertness and preparing the body for the demands of the day.
A 2024 étude en Revues endocriniennes found that wake time (what time you wake up), mentally preparing for the next day’s events, and one’s mood from the prior day regulate the CAR for the next day, affecting emotional regulation, brain plasticity, cognitive functioning, immune regulation, and energy production [2].
What does cortisol do for you?
- It regulates your metabolism
Cortisol plays a central role in the regulation of glucose metabolism, particularly in relation to exercice. It stimulates gluconeogenesis (the production of sugar from fat and protein sources, mostly by the liver), ensuring that the body has an adequate supply of energy during times of acute stress. Cortisol also adjusts the metabolism of fats, proteins, and carbohydrates, influencing body composition, blood glucose and insulin levels, and energy expenditure [3].
- Cortisol helps with immune function and inflammation
The HPA axis produces cortisol as a reaction to acute exposure to stress (short bursts that quickly fade) and enhances the activity of white blood cells as well as pro-inflammatory cells. These cells play a crucial role in the initial immune response to infection or injury, and recruit other immune cells to the site of injury [4].
However, in a state of chronique stress, these pro-inflammatory cells can cause harm, a decrease in the body’s ability to fight off infection and illness, and increased vulnerability to diseases like arthritis, heart disease, and cancer [4].
- Cortisol aids cardiovascular health
Cortisol affects cardiovascular health by regulating blood pressure [5]. Cortisol enhances the sensitivity of blood vessels to vasoconstriction (when blood vessels get smaller, which increases blood pressure–imagine drinking through a cocktail straw compared to a regular straw).
Selon la Association américaine du cœur, “In a study of more than 400 adults with normal blood pressure, those who had high levels of stress hormones detected in their urine were more likely to develop high blood pressure over the next 6-7 years.” High blood pressure is in turn linked to an increased likelihood of heart attacks and strokes.
- Cortisol helps regulate mood and improve cognitive function
In the brain, cortisol plays a role in mood regulation, memory, and cognitive function. Short-term increases in cortisol help the body to respond to stress effectively, enhancing memory and alertness [6].
Chronically elevated cortisol is linked to mood and cognitive disorders and metabolic issues
Mood and cognitive disorders
Despite its positive acute effects, chronically high cortisol levels can impair cognitive function and are linked to mood disorders such as anxiety and depression [7]. Chronic stress and elevated cortisol are associated with hippocampal shrinking (the hippocampus is the part of the brain responsible for memory formation and consolidation).
A 2023 study in Frontiers in Aging Neuroscience found that cortisol levels were significantly higher in older adults with Alzheimer’s Disease compared to healthy elders. “Higher cortisol levels were significantly associated with smaller left hippocampal volumes in [healthy seniors] and indirectly negatively correlated to memory function through hippocampal volume. Higher cortisol levels were further related to lower gray matter volume in the hippocampus” [7].
Metabolic disorders
Persistently high cortisol levels are also associated with metabolic disorders, y compris résistance à l'insuline, obesity, and type 2 diabetes. Not only does stress affect behaviors like overeating and overconsumption of foods high in sugar and fat, but it also tends to shorten sleep and decrease physical activity, leading to an increase in obesity [8].
Additionally, elevated cortisol levels can cause muscle breakdown and osteoporosis. Cortisol is a catabolic hormone. This means, as previously mentioned, that it breaks down fats and proteins to use as energy. In times of chronic stress, cortisol may lead to the breakdown of skeletal muscle and bone to turn into the energy needed to maintain the stress response, leading to reduced mobility and increased likelihood of injury [9].
Sometimes cortisol disorders ne sont pas stress-related
There are several cortisol-related disorders that ne sont pas caused by stress, though they do affect the body’s ability to process stressful situations. The two most common ones are Cushing’s syndrome and Addison’s disease.
Cushing’s syndrome is a disorder characterized by excessive cortisol production. Adrenal insufficiency, or Addison’s disease, is a condition where the adrenal glands do not produce enough cortisol.
Les deux conditions arise from dysregulated cortisol secretion. Cushing’s syndrome can lead to a range of symptoms, including weight gain, hypertension, and ostéoporose. Addison’s disease, on the other hand, can lead to fatigue, muscle weakness, and low blood pressure.
How does cortisol interact with your reproductive hormones?
Excess cortisol can affect every aspect of health, including hormonal and sexual health. Irregular menstrual cycle, baisse de la libido, and mood changes can be a sign of changing hormone levels due to increased stress.
Testostérone
While mainly thought of as a male hormone, testostérone plays a vital role in women as well, because it’s necessary for developing and maintaining muscle mass, producing blood cells in bone marrow, regulating metabolism and cholesterol levels, improving sleep quality, and supporting libido.
Elevated cortisol levels due to chronic stress may decrease testosterone [10]. A decrease in testosterone levels in women can lead to obesity, muscle loss, poor sleep, decreased bone density, joint pain, and even infertility.
Œstrogènes
The relationship between œstrogène and cortisol can be a two-way street. When a woman is under high stress, whether physical or emotional, her body may perceive that it’s not a good time to ovulate. Consequently, it may tamp down on its production of estrogen, which typically rises dramatically before ovulation. Decreased estrogen levels secondary to chronic stress can lead to the same side effects as menopause–hot flashes, night sweats, fatigue, and irregular periods.
On the other hand, high estrogen levels caused by synthetic estrogen medications can lead to an increase in cortisol levels, as occurs with hormonal birth control (more on this below).
Progestérone
In general, when cortisol levels rise, so does progestérone production [11]. However, chronique stress is associated with low les niveaux de progestérone and all the accompanying symptoms, such as irregular periods and abnormal bleeding, migraines, weight gain, lower libido, mood swings especially with anxiety and depression, and increased susceptibility to fibromes utérins.
Interestingly, the relationship between chronic stress and lowered progesterone appears to be a result of upstream HPA axis changes (remember that the HPA axis controls multiple hormonal cascades, not just cortisol production) and not due to the elevated cortisol levels en soi [12].
Cortisol and hormonal birth control
Insights from Votre cerveau sur le contrôle des naissances
In a book that’s been making waves on the internet over the past few years called Votre cerveau sur le contrôle des naissances, evolutionary psychologist Sarah E. Hill, PhD, explains how and why women on hormonal contraceptives have altered stress responses compared to women not taking HBC.
As Natural Womanhood previously quoted in our article “La pilule et le stress : Comment la contraception hormonale peut vous rendre la vie plus difficile,” Dr Hill notes that:
“The Pill-taking women’s pattern of HPA-axis function looks suspiciously similar to that of someone who has experienced chronic stress, suggesting that the Pill might actually cause the HPA axis to go into overdrive, requiring it to [eventually] take coordinated action to blunt itself.” (You can read more about Hill’s book ici.)
Hormonal birth control can impact your prefrontal cortex, which regulates emotional response
A 2023 study by the University of Quebec published in Frontières de l'endocrinologie (and as expanded on in this Natural Womanhood article) looked at the ventromedial prefrontal cortex (vmPFC) of women on HBC, women that have never used HBC, and men as an added control group. The researchers noted, “this part of the prefrontal cortex is thought to sustain emotion regulation, such as decreasing fear signals in the context of a safe situation” [13].
Notably, the researchers found that the women using hormonal contraceptives had thinner vmPFCs compared to both men and never-using women. The researchers concluded “Our result may represent a mechanism by which [HBC] could impair emotion regulation in women” [13].
For even more on the relationship between HBC and stress, check out the following Natural Womanhood articles:
- La pilule et le stress : Comment la contraception hormonale peut vous rendre la vie plus difficile
- Contraception hormonale, inflammation, humeur et stress : Quel est le lien ?
- La "fatigue surrénale" n'est peut-être pas réelle, mais la dysrégulation de l'axe HPA l'est bel et bien.
The bottom line on cortisol: Too much of a good thing can be harmful to metabolic, immune, cognitive health
When it comes to cortisol, too much of a good thing can be harmful to metabolic, immune, and cognitive health. On the one hand, cortisol is a vital hormone involved in regulating a wide range of physiological processes, from metabolism to immune response. However, when cortisol levels are chronically elevated, especially due to prolonged stress, various health problems, including metabolic disturbances, immune suppression, and cognitive decline, may result.
Managing stress, quitting hormonal birth control, exercise, and leading an overall healthy lifestyle can help keep cortisol levels within normal range, in the “sweet spot” for optimal functioning.
